TORONTO — The heads of two of Canada’s biggest unions say they’re resigning so new leaders can take the helm and expand the membership rolls as the groups join together in a merger that will create the country’s largest private-sector union.

Canadian Auto Workers national president Ken Lewenza and Communications, Energy and Paperworkers Union of Canada president Dave Coles said Thursday that fresh leadership is needed as the combined union — named Unifor — reaches out to new workplaces as well as students and those left on the economic wayside.

Lewenza, a leading voice for organized labour, said he’s been torn for months on whether to run for president of Unifor, which came together last October with the sign-on of the CEP.

But looking at a possible “six or seven” year commitment as the group fully takes shape, he decided it was time to step aside.

“I asked myself, do I want to start a job and recognize that I can’t complete the job,” Lewenza, 59, told reporters in Toronto.

“I’m retiring because it’s in the best interest of my union.”

Coles said the time was right for a “new team” to lead Unifor and fight back against what he called attacks on labour by the federal government.

Both Coles and Lewenza are backing senior CAW member Jerry Dias to lead Unifor.

“It is an absolute golden opportunity for myself and brother Lewenza to pass the torch,” said Coles.

Unifor will initially represent more than 300,000 workers across roughly 20 sectors of the economy, primarily in manufacturing, communications and transportation, as well as some public sector employees in the health, education and transit sectors.

It plans to devote 10 per cent of its revenues to organize workplaces and add new members, while also hammering out a mechanism that will allow students, retirees, the unemployed and others to join — something “that’s never been tried before,” said Coles.

Lewenza said he would stick around as an “ambassador” for Unifor, and speak out on economic issues such as income security and unemployment.

Coles has been president of the CEP since 2006, while Lewenza was elected the national president of the CAW in 2008, replacing Buzz Hargrove.

Unifor will choose its leadership at a convention set for Labour Day weekend. Lewenza and Coles said they will retire effective Oct. 1.

Dias said he isn’t taking the endorsement for granted, noting that members will have their say at the union’s founding convention, where Unifor’s constitution, name and logo will also be approved.

“I’m pleased but I’ll be happier in September,” said Dias, a former aircraft plant worker who has served as national president assistant to both Lewenza and Hargrove.

Lewenza said Unifor aims to sign up non-traditional members and help them gain stable employment and benefits like those won by union members over decades of hard-fought battles and collective bargaining negotiations.

“I don’t see the difference between the needs of our membership and the needs of Canadians. Unions are about establishing balance, about winning for the middle class, about winning opportunity and winning a reasonable standard of living with a reasonable work life.”